A. Field of the Invention
The present invention relates generally to compositions that can be used to improve the skin's visual appearance. In particular, the present invention concerns topical skin care compositions that include kakadu plum (Terminalia ferdinandiana) extract and/or acai berry extract (Euterpe oleracea).
B. Description of Related Art
With ageing, chronic exposure to adverse environmental factors, or malnutrition, the visual appearance, physical properties, and physiological functions of skin can change in ways that are considered visually undesirable. The most notable and obvious changes include the development of fine lines and wrinkles, loss of elasticity, increased sagging, loss of firmness, loss of color evenness or tone, coarse surface texture, and mottled pigmentation. Less obvious, but measurable changes which occur as skin ages or endures chronic environmental insult include a general reduction in cellular and tissue vitality, reduction in cell replication rates, reduced cutaneous blood flow, reduced moisture content, accumulated errors in structure and function, alterations in the normal regulation of common biochemical pathways, and a reduction in the skin's ability to remodel and repair itself. Many of the alterations in appearance and function of the skin are caused by changes in the outer epidermal layer of the skin, while others are caused by changes in the lower dermis.
Several different approaches have been used to treat damaged skin caused by aging, environmental factors, chemicals, or malnutrition. One approach involves the use of specific agents to directly stimulate or inhibit selected biochemical targets. Examples include the use of retinoids to stimulate collagen and glycosaminoglycan synthesis by fibroblasts (Schiltz, et al., 1986). Another approach is to use agents or processes that stimulate the rate at which the epidermis replaces itself, a process known as epidermal cell renewal. Increases in epidermal cell renewal rates usually result from a more rapid rate of replication of epidermal basal cells, and can be caused by diverse stimuli such as chemical or physical injury, adverse environmental conditions, or direct stimulators of basal cell division.
Some examples of chemical injury include allergic or non-allergic contact irritation, pH extremes, or interaction of the stratum corneum with household or industrial chemicals or pollutants. Physical injury can include skin abrasion, friction (i.e. on the soles and heels of the feet), or removal of the stratum corneum by physical exfoliation (i.e. cosmetic masks) or by tape stripping. Agents that directly or indirectly stimulate basal cell division include retinoids and barrier disrupters. For example, U.S. Pat. No. 5,720,963 discloses that a combination of hydroxy acids, retinoids, and cerebrosides causes chronic injury to the stratum corneum and results in epidermal and dermal repair of the structurally-deteriorated skin. U.S. Pat. No. 6,495,126, for example, uses a combination of surfactants and chelating agents to stimulate an endogenous stratum corneum chymotryptic proteinase that causes a loosening of corneocytes, resulting in an increased rate of epidermal replacement and chronic anti-aging benefits. Adverse environmental exposures that can result in more rapid epidermal turnover rates include UVA, UVB, and IR radiation from the sun and cold coupled with low relative humidity (i.e. low dew point).
Several of the above methods have been shown to have various drawbacks, such as significant irritation to the skin or skin toxicity. In addition, most of these methods involve the invocation of chronic damage to the skin, which sets up repair mechanisms. For most of the existing treatments, there will be a period of time, up to several weeks or months, during which the skin becomes irritated and after which tolerance sets in and the symptoms of irritation may decrease and/or cease.